1. Field of the Invention
The present invention relates generally to placement of substantially non-flowable cementitious material in an underground space, and more particularly, to methods of admixing and placing the substantially non-flowable cementitious material into an underground space, such as a mine shaft or the like.
2. Description of the Prior Art.
Cementitious materials, such as API cements and blends of API cements with fly ash, such as "POZMIX.RTM." cement, are widely used in the industry. These materials are typically pumped in a liquid state and designed to flow and to harden after placement. Cement slurry is often used in wellbores to protect fresh water zones from hydrocarbons and/or brine water contamination, to isolate hydrocarbon bearing formations, and to protect tubular goods from corrosive gas and fluids. Furthermore, it is desirable to use cementitious materials for plugging abandoned underground spaces, such as mine shafts or the like.
Current methods of placing flowable cementitious materials in underground spaces, such as mine shafts, are inefficient and uneconomical because the flowable material is often wasted by entry into vugular porosity, natural fractures, weak formations, and other undesired areas. Typically, an excess volume of cement slurry is calculated without certainty that the calculated fill up volume will be accurate. Therefore, due to the waste and loss of cementitious materials into unwanted areas, it is undesirable to use flowable materials for filling mine shafts or the like.
However, use of substantially non-flowable (zero inches slump) cementitious material is desired for filling underground spaces, such as mine shafts, because the material does not flow away from the area of placement. Therefore, less waste occurs into unwanted areas and fill up volumes are more accurately calculated.
Until now, no method has been provided for plugging underground spaces with substantially non-flowable cementitious material. Thus, there is a need for methods of admixing and placing substantially non-flowable cementitious material into an underground space, such as a mine shaft or the like.